In an information recording process on a writable or rewritable optical disc such as a DVD-R (DVD-Recordable) or DVD-RW (DVD-Re-recordable) as an information recording medium having large recording capacity which is used more and more commonly in recent years, a laser power control method of forming recording pits with a laser pulse train including a plurality of short laser pulses is used. Such a method is also called a write strategy method.
The laser pulse train is made of a plurality of laser pulses whose amplitudes vary between a predetermined read power level and a write (recording) power level. Specifically, according to a recording signal, in a region (hereinbelow, also properly called “space part”) on a recording surface of an optical disc in which no recording pits are formed, the recording surface is irradiated with a laser beam at a read power. In a region (hereinbelow, also properly called “pit part”) on a recording surface in which recording pits are to be formed, the recording surface is irradiated with a laser beam at a power according to a laser pulse train whose amplitude varies between the read power and the write power, thereby forming recording pits on the recording surface.
In recent years, as an example of the write strategy method, a technique disclosed in Patent Document 1 has been also proposed. Patent Document 1: Japanese Patent Application Laid-open No. 2003-85753 (FIGS. 5, 6, and 12)